Welcome to the weather blog - a regular Monday through Friday discussion of the weather! While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants. I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible. You'll find a quick weather synopsis and a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. My email is contact@mattnoyes.net. This blog is for you, so I hope you enjoy it! -Matt Noyes
For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net
Matt's Quick Weather Synopsis:
SATURDAY UPDATE: Just a quick update to let you know I'm here and checking in...and I think the forecast will fall within about an inch of the numbers on the map posted below from yesterday (Friday) morning. There are likely to be a few 6" amounts coming back, and up to 7 or 8 in the higher terrain of the 5+ area, but average amounts should still fall very close to what's been posted. Enjoy the storm...nice to have it be big enough to see the snow, but small enough that I can enjoy it from home...a rare treat for a broadcast meteorologist! Be sure to check out Joe Joyce with his coverage on NECN if you can!
Friday's Post: Areas of black ice on roadways greet commuters of secondary roads and exit/entrance ramps to some highways Friday morning as scattered showers of rain and snow Thursday afternoon and night have left plenty of moisture in some spots. Heavier snow squalls are moving east through Maine, where they will set up shop in Eastern Coastal Maine through Friday afternoon, delivering 3"-4" of snow in this area. Elsewhere, mountain snow squalls will float through Northern and Western New England today while the remainder of New England finds a very gusty northwest wind bringing in enough dry air for plenty of sunshine and just a few scattered flurries. Wind gusts may reach 55 mph Friday afternoon in some communities around New England and this means isolated damage to trees, tree limbs and power lines are possible - nothing like last Friday's damaging winds that gusted to 70-80 mph, but isolated damage is possible today nonetheless. Expect winds to subside Friday night under mostly clear skies and a cold night. A storm located over the Northern Plains Friday morning will move over New England later Saturday, blotting out any early morning sunshine behind increasing clouds, with light snow developing either side of 2 PM across New England and becoming heavier around 5 PM and lasting until around midnight with plowable snow for many (see accumulation maps below). After snow ends late Saturday night, expect a drier, brighter, but cold and blustery day on Sunday as an arctic airmass pours into New England. Cold air will remain in place on Monday, though another approaching storm will thicken the clouds and allow for snow to develop late and at night. I'm expecting the cold and wintry feel to continue through next week! -Matt
Accumulation Map for Saturday/Saturday Night Snow:
General Weather Summary: After heavy snow and rain squalls for some communities later Thursday into predawn Friday, black ice found on secondary roadways, walkways, and exit/entrance ramps to some highways will melt away after making for a few Friday morning slick spots. Exceptions will continue to be found in Eastern Maine where a weak area of low pressure will keep snow squalls falling through the day for 3"-4" of accumulation in Coastal Washington and Hancock Counties, and in the mountains of Northern and Western New England where scattered snow showers and squalls will continue to blow through. Otherwise, expect a very gusty northwest wind to usher in cold and dry air for most of New England, bringing out plenty of sunshine amidst just a few isolated flurries, but also bringing wind gusts to 55 mph for some communities, which will be sufficient to cause isolated damage to trees, tree limbs and power lines. It's important to note that while the wind will be capable of causing damage, blowing light objects around and pushing your car around a bit on the road, they will be nothing like the prolonged and intense damaging wind event of one week ago today.
Today's busy winds come as New England is sandwiched between a departing area of low pressure to our northwest and a bubble of high pressure building in from the west. With a very fast flow in the atmosphere, this high pressure, fair weather center will build in quickly overnight Friday night and winds will subside with clearing skies for most areas as it does. This combination of lighter wind and clearing skies will allow temperatures to drop into the single digits north and teens south Friday night.
Saturday likely dawns with some limited sunshine ahead of a fast-moving storm center traversing the nation and taking aim on New England. Though the storm came ashore from the Pacific in the Pacific northwest on Thursday and was located over the Northern Plains Friday morning, it will be racing east and already spreading clouds into New England Saturday morning. By mid-afternoon Saturday - likely sometime around 2-3 PM - light snow will begin falling in many parts of New England, becoming steadier and heavier by 5 PM. This snow will not come down for very long thanks to the fast winds aloft pushing the storm through quickly, but will come down heavily at times Saturday evening and the first part of Saturday night, with widespread accumulations of 4"-5" by midnight Saturday night (see accumulation maps above), with local amounts to half a foot and lesser amounts to the north and south of the heaviest band of precipitation. The snowfall accumulation forecast you see on my map is the result of two factors to be considered: 1) The shape of the snowfall pattern is defined by the rapid increase of warmth and moisture moving in from southwest to northeast in the south winds ahead of the counter-clockwise storm circulation, and 2) The amounts are based on somewhere around or just over 1/4" of melted precipitation in most areas in the heart of the precipitation band, but cold temperatures aloft will allow for a fluffy snow, so snow will pile up quickly and easily.
Again dictated by the fast jet stream winds aloft in the atmosphere, this storm will keep on truckin' and snow will end around midnight in most areas. Winds will once again become quite active from the northwest and north behind this storm, and those winds will tap a well of cold Canadian arctic air that will come screaming in on Sunday, holding temperatures in the lower 20's through Southern New England and teens for Central and Northern areas. With a biting wind, wind chill values will feel a good 8-12 degrees colder than the actual highs! A few flurries and snow showers will still be possible in the mountains, though most of New England is likely to stay mainly dry.
Cold air sticks around into Monday and beyond, as the atmospheric pattern features something special in the world of meteorology...a developing "Greenland Block." This is the term meteorologists use to describe a large and stationary area of high pressure that builds across Greenland - well to our east - and because high pressure is generally a fair-weather center, it blocks storms from moving quickly across the North Atlantic. The result is to keep storms curling north when they move just east of the Canadian Maritimes, and with counter-clockwise flow of air around storms, this keeps an average northerly wind blowing into New England for quite some time. The result of a pattern like this is for cold conditions to persist, with storms reaching their maximum intensity to our east, rather than over us, but that's not to say storms can't still affect New England - just like what's happening this weekend, stronger disturbances can occasionally strengthen further as they move overhead and this can produce widespread snows. A similar situation may be in the cards for Monday night, then several chances of disturbed weather will remain while this "Greenland Block" holds.
Enjoy your weekend - I'll be back with you on Monday!
Matt
Matt's Technical Meteorological Discussion: Updated Friday, February 24 at 10:20 AM
Upslope snow squalls will continue in the Green Mountains in cold advection upslope flow today, and Champlain Valley is also reaping the benefits of a WNW flow until wind veers more to the NW later today. Amounts in the higher terrain will near 10" in the Central and Northern Greens where the squalls stay put, a few inches of accumulation elsewhere up the spine of the Greens and away from the higher summits. Squalls moving across the Maine Turnpike Fri AM are the result of a vorticity maximum and associated weak developing surface wave which, as of this writing, is moving SE across Penobscot Bay. Once this circulation hits the waters of the Gulf of ME, agreement among the guidance is for stationary/slow moving band of snow squalls to set up over or near Coastal Washington and Hancock Counties and with QPF nearing .25" (perhaps a bit overdone, and the chance it will miss and set up over the ocean) I've gone with a few inches possible in immediate coastal locales in this area. Elsewhere in NewEng, mixing to about 880 mb by the end of the day and this will tap an increasing cold llvl jet screaming around the base of the vort max moving N of NewEng and evident on morning satellite imagery. This jet streak extends low enough to encounter our well mixed layer with about 50-55 kts of NW flow, and damaging wind gusts to 55 mph will be possible in some areas. Nothing like the event of exactly one week ago today, but capable of isolated damage and disruption.
Subsidence between shortwaves and associated with splitting high pressure cell means clearing skies Fri Ngt with diminishing winds as surface ridge axis shifts over NewEng and this will set us up for decent radiational cooling with single digits in the north and teens south, and of course will ensure - as if we needed it - that temperatures region-wide will be plenty cold enough for snow with the next system on Saturday.
As for this system, it's been much talked about here for a few days, and perhaps the most remarkable part is the lack of change in the guidance from one cycle to the next. Of course, that's to be expected in this pattern - a well-defined fast flow that features strongest cyclogenesis to our east. A few storms earlier this year I remarked here how we were in the most difficult part of the pattern to accurately forecast - just ahead of the mean trof positon. Now, being just behind it, we will find differences in the guidance usually only pertaining to timing, and that has been the case this time around, but I still think we're on target for the faster Saturday afternoon timing laid out yesterday, and at this point it looks like clouds race in Sat AM ahead of what is still very impressive speed convergence ahead of llvl jet punching north and northwest into NewEng during the day. This teams up with intense cyclonic vorticity advection ahead of 30-35 unit vorticity maximum that dives SE across Central and Southern NewEng Sat afternoon and eve. As mentioned yesterday, I truly believe it's the combination of this strong CVA, coupled with what's going on especially in the lower levels of the atmosphere that will drive the evolution of this storm. Somewhat of a center jump appears to be in the cards for the surface low with this fast moving vort, but the shortwave is strong enough as it comes through that dynamic forcing will make this center jump a help rather than a hindrance when it comes to snow production, as it will enhance low level easterly flow ahead of the center of the vort max, and therefore enhance available moisture thanks to Atlantic inflow. QPF is well agreed upon for the broad swath of over .25" among virtually all guidance, with center of the band closer to .40". Temps aloft are actually a bit too cold for ideal ratios, so somewhere around 15:1 looks reasonable. What's scary is that this keeps snowfall amounts right where you and I them two days ago in this discussion at about 4"-6" in a large swath of NewEng. Given the limited area of .40" QPF amounts in only the heart of the band, I've opted to go 4-5" in my broadcasts for this area, with obvious orographic enhancement in the appropriate areas. Also important to note that SE flow will mean a shadow effect for parts of West-Central NH, and for parts of the Northeast Kingdom of VT - I've tried to indicate that on the maps. Even though I'm still expecting bursts of heavy snow in the heart of the isentropic lift Sat eve, especially during passage of the vort, there's absolutely no question that this is a fast moving system, and snow will not last longer than from about noon (west) and 2 PM (east) to around midnight most areas. So, considering the short duration, these snowfall amounts become even more impressive.
After the storm departs around midnight Sat Ngt (perhaps eastern areas with snow lingering longer thanks to marine airmass contrasting with incoming arctic air, which has a tendency to wring moisture out as snowflakes), arctic airmass still expected to unload on NewEng with 850 temps dropping to -18 C Sunday and NNW wind direction - one of the coldest for NewEng. Fighting the build of surface cold will be the fact that high pressure stays put to our east, so this cold truly has to build down from aloft, but there's enough of it to get 925 mb temps -12 to -13 C Sunday, and equally cold if not a tad colder Monday as the flow tries to turn SW but has to wait for weak shortwave ridge axis to pass, and once that SW flow does come in, clouds increase quickly.
This leads us into our next shortwave with potential, which is slated for Mon Ngt. Again, timing on this may end up speeding up a bit, and NAM is already indicating that in its new 12Z run. And while I'll acknowledge this shortwave has potential, I'm not willing to bite too hard on it yet, as steering flow is very much a NW flow with mean trof position shifting E of NewEng as polar vortex effective shifts to a position NE of ME. This, in conjunction with the strong building Greenland block position and an NAO that will tank over the coming week and really for the first 7-10 days of March, will keep the storm breeding ground east of us, so it's going to take strong shortwaves, AND some flattening of the flow east of us - usually in response to shortwave ridging ahead of the disturbances - to get these systems to amplify. So, for now, we'll keep an eye on the Monday/Monday night vorticity maximum and see how it evolves. The one behind it may have more potential for midweek. Regardless, a good meteorologist will stay on guard at all times in the aforementioned pattern, as it won't take much to organize something nearby, and it's also important to note that when the NAO finally does switch from strongly negative to neutral or even positive - which is somewhere around the 7th or 8th of March - research suggests major precipitation producing storms are often found with such NAO signal shifts, especially coming out of a pattern like the one we're in now. Food for thought.
Enjoy your weekend and good luck with your snow forecasts!
Matt
